Variable pitch propeller



March 1, 1932. p. E. 'GLAFCKE 1,347,180

VARIABLE PITCH FROPELLER Filed July 12, 1930 gmwntoz 6 faui f/afww.

Patented Mar. 1, 1932 UNITED STATES PATENT OFFICE PAUL E. GLAFGKE, or DENVER, coLoiamo VARIABLE Prrcn 2302mm Application filed m 12. 1930. Serial No. 467,518.

This invention relates to improvements in variable pitch propellers of the type employed in connection with aeroplanes and airships.

5 It has long been recognized that very .desirable results could be obtained if the propellers used onaeroplanes were so constructed that the pitch of the propeller blades could be varied by the pilot in such away that he could utilize the most effective pitch for starting and after the aeroplane has reached the desiredelevation, be able to change the pitch to the one most suitable for traveling.

I am aware that different mechanisms have been provided for effecting a change of pitch in the propeller blades while the propeller is rotating, and I do not claim to be the inventor broadly of means for this purpose, as this invention relates more particularl to an improved construction of means or such a purpose.

It is the object of this invention to produce =a mechanism for changing the pitc of propeller blades while they are rotat' g and which shall be light and of simple'construction and composed of a few parts that can be made very strong and substantial and which will also develop a great amount of power when in operation.

Another object of this invention is to produce a propeller construction in which the 'propeller blades shall be provided with hol-. low root portions that slide over cylindrical arms that are formed integral with the hub and which are provided with worm gears on their outer circumference and held onto the radial arms by means that prevent them from flying off from the hub when the latter is rotated and which also permits theblade to Another object of this invention is to provide a propeller of the variable pitch type with an effective and simple means for holding the propeller blades in place on the hub while permitting them to be quite readily rotated about their 10 itudinal axes for the purpose of varyng their pitch.

The above and other objects of this invention that may appear as this description pro- I ceeds are attained by means of a construction rotate about the radial arms of the hubs.

Fig. 1 is an end view of my improved variable pitch propeller, the outer ends of the blades being removed;

Fig. 2 is a view showing the.propeller hub 00 in side elevation with parts broken away to better disclose the construction;

F Fig. 3 is a section taken on' line 33,

F ig. 4 is a section taken on line 4-4, 66

ig. 2; Fig. 5 is a view partly in section and partly in elevation showing one means for securing the blades of a variable pitch propeller to the hub portion; and V 70 .Fig. 6 is a perspective view of the central portion of my improved propeller.

In the drawin s reference numeral 1 represents the propeller shaft to which the hub 2 is secured in the usual way. In the example '15 illustrated, a two-blade propeller has been shown and the hub is therefore provided with two arms 3 that extend radially from the hub and which are in axial alignment with each other. Secured to the hub are two propeller blades that have been designated by reference numeral 4 and which are provided with cylindrical, hollow root portions 5, the openings of which are of such size that they receive the arms 3 with a snug sliding fit. The

inner ends of the root portions are provided with integral worm wheels 6, for a purpose which will hereinafter more fully appear.

For the purpose of holding the blades attached to the hub and at the same time per- 99 mitting them to be rotated about the axes of arms 3, the latter have been provided with circular grooves 'Z and the inner surfaces of the openlngs in the root portions have been provided with annular grooves 8 of the same width as the grooves 7 The root portions of the blades are also provided with a removable section 9 that can be removed for the purpose of permitting a band 10 containing a plurality of steel blocks 11 to be introduced into the grooves 7 and 8 and which, when in place, positively holds the two parts against withdrawal in the direction of the axes of arms 3, but permits the blades to be rotated. The closure 9 may be put in place and is held in place by means of pins 12 that extend into corresponding openings 13 in the opening for which member 9 forms the closure and the other end of member 9 is provided with a projection 14 that extends into a depression 15 and which is perforated for the reception of a pin 16 that holds the closure in place. the'openings in the root portions of the blades are carefully ground so as to make a perfect fit with the arms 3 and so as to permit only a thin film of oil between the surfaces, the blades can be quite readily rotated, even when the propeller is rotating at maximum speed, because the close fit of the part, as well as the large area in contact prevents the formation of pressure areas where the oil film is reduced to such an extent that friction becomes excessive as is oftentimes the case where the parts are not properly fitted, and where the bearing area is too small.

For the purpose of rotating the propellers about their axes while they are turning about the axis of shaft 1, a specific mechanism has been provided which will not be described. The propeller hub is provided on opposite sides with outwardly extending lugs 17 that are perforated for the reception of clamping bolts 18. Secured to the lugs 17 are two plates 19 and 20. These plates are provided with central openings for the reception of shaft 1 and are held inposition by means of bolts 18 and also by the action of nut 21 that is threadedly secured to the outer end of the propeller shaft. A washer 22 separates the inner surface of the nut from the outer surface of plate 20. The outer ends of plates 19 and 20 are provided with notches 23 and the projecting portions 24 on opposite sides of the notches are each provided with semicircular recesses which form bearings for the shafts 25. These shafts have formed integral shown in with them, worms 26 that are located in the notches 23 and whiclT cooperate with the worm gears 6 on the inner ends of the root portions of the hub. Shafts 25 are provided on their outer ends with worm gears 27 that are engaged by worms 28 carried by shafts 29. The front ends of shafts 29 are journaled in bearings formed in the lugs 30. The rear ends of shafts 29 are journaled in bearings formed in plate 31 that issecured to the inner end of the hub. Secured to the rear ends of shafts 29 are star wheels 32 that are usually provided with four radial arms 33 like those Fig. 4, but which may have a greater number of arms depending on the particular results desired. Secured to shaft 29 on the front side of plate 31 are notched wheels 34, whose outer surfaces are provided with notches 35. Spring pawls 36 are fastened to the plate '31 at points 37 and have f vided with a radial flange 41 that forms a stop which limits the rearward movements of the pins, and the other ends are provided with soft iron plates 42 that serve as armatures and which are separated from the ends of the solenoids by means of springs 43 that are normally under compression and tend to hold the pins in the position shown. Pins 40 are so located that if they are projected while the-propeller is rotating, they will extend into the path of arms 33 of the star wheels 32 and the latter will be caused to rotate a fraction of a revolution every time it hits one of these pins. One pin is located nearer the axis of shaft 1 than the other, and therefore when the pin that is nearest the axis of shaft 1 is projected into the shaft of the rotating star wheels, they will be rotated in one direction, "while if the other pin is projected into the path of the star wheels they will be rotated in the opposite direction, for the reason that one pin lies between the loci of shafts 32 and the center of the shaft 1, while the other pin lies to the outside of these loci and consequently tends to turn the wheels and the shafts 29 in opposite directions. When the solenoids 39 are deenergized', pins 40 will remain in inoperative position, but by energizing either one of the solenoids, the corresponding pin will be moved forwardly into the path of the star Wheel and will rotate the same. In the example shown, each star wheel has four arms and the parts are so adjusted that every time it strikes a pin it is rotated through an angle of 90 degrees and therefore shafts 29 will each be rotated through a quarter of a revolution each turn of the propeller shaft. As shafts 29 are rotated, the worms 28 which are also rotated transmit this rotation to worm. wheel 27 whereby the shafts 25 and worms 26 are rotated, thereby producing a corresponding rotation of the propeller blades. Since there is a large speed reduction between the shafts 29 and the propeller blades, it is evident that the propeller blades will only rotate through a very small angle each revolution of the propeller shaft, and therefore the propeller blades are turned slightly but positively by power derived from the engine. As soon as the desired angles are obtained, the solenoids are deenergized and the parts returned to inoperative or normal position.

Plates l9 and 20 are provided with openings for the reception of dowel pins 44 that serve to properly align .the plates and are secured to the hub by stud bolts 45 that are in addition to bolts 18 already referred to.

In Fig. 5 I have shown a modified form of construction for the purpose of securing the propeller blades to the hub. In this construction the radial arms 3a are provided with extensions 46 of somewhat smaller diameter and the outer ends of which are threaded as indicated by reference numeral 47. The root portions of the blades are provided with openings of. the proper size to receive the "arms 3a and theouter ends of these openings are reduced in diameter so as to receive the parts 46 in the manner shown in Fig. 5. The blades are each provided with a port or an opening 48 into which the end of the corresponding member 46 projects. A saddle or plate 49 extends crosswise over the inner end of opening 48 andhas its ends bent downwardly in the manner shown in the drawings. Supported on this plate is a raceway 50 on which the conical rollers 51 travel. Another raceway 52 surrounds the cylindrical part 46 and is held'in place by means of a nut 53 that after it has been properly tightened, is held against rotation y means of a pin 54, or other equivalent means. The centrifugal force that is developed by the blades when they are rotating is resisted bearing in place, and since the largest amount of force produced during the operation of the propeller is the centrifugal force, and since this is taken care of by roller bearings, the blades may be quite readily turned about their axes by means of the mechanism above described. For the purpose of strengthening the blades to make up for the loss of strength due to the formation of openings 48, the sides of the blades have been enlarged on opposite sides of these openings, as indicated by reference numeral 55. With the construction shown in Fig. 5, blades can be very easily removed and replagad whenever this is found to be necessary. It is only necessary to remove nut 53, whereupon the blade can be readily removed from the arm 3a in a manner quite apparent from Fig. 5.

Likewise and in contradistinction to the current practice of clamping propeller blades in radially projecting sleeves integral with the hub where change of pitch may be made on the ground by loosening the clamps and resetting the blades, the form shown in Fig. 5 may be utilized in the same manner by dispensing-with the cone or ball bearing assembly and jamming the nut so as to hold the parts rigidly at the position or setting desired.

by the nut 53 which holds the roller readily adjustable as such to very precise performance yet easily shifted as a unitto permit quick replacement or adjustment of the propeller blades.

Manifest advantages result in skirting outer lower edge of the hollow blade butt with an encircling worm gear permitting it to rotate axially completely about the hub projections as shown, for thereby an increased and increasable radial leverage is attainable with an accessibility to parts superior to that restrictive practice where a solid blade butt is carried within hollow or cylindrical radial projections on the hub in which weakening openings are required for the mechanical engagement of parts within and on the butt.

It is my intention to equip the apparatus shown on the drawings and described herein with electrical means for indicating the position of the propeller blades so that the pilot may at all times be advised of the pitch angle, but since this involves a different invention, it has not been shown and described herein.

I want to call attention to the fact that instead of using electromagnetic means for moving pins 40, other suitable means, such as cables or levers may be employed, and the electromagnetic means shown is therefore not to be considered a limitation, but rather as illustrative of a means for effecting the purpose under consideration.

' The essence of this invention resides in a simple mechanism embodying a componental and complemental arrangement of worm gears, worm and pinions of suitable size, number of teeth, threads, etc., that transmit, while the propeller is in operation, light impulses from the source cumulative to great power in effecting a change of pitch of the blades without great strains and within definite and controllable time periods as qualified by the revolutions per minute of the propeller and all this with little added torque on the propeller shaft or between the front of fuselage and the propeller.

Having described the invention what is claimed as new is:

1. A variable pitch propeller comprising, in combination, a drive shaft, a hub secured to the front end thereof, said hub having a plurality of radially extending cylindrical arms, a propeller blade secured to each arm,

each blade having a tubular root portion adapted to receive an arm, means for holding the blades against longitudinal movement on the arms .while permitting rotary movement, the root portion of each blade having a worm gear on its exterior, a worm shaft rotatably secured to the hub with its axis in theplane of the worm gear, a worm' carried by the shaft, there being a separate worm shaft and worm for each blade, a worm gear secured to one end of each worm shaft, a second worm shaft and worm operatively associated with the worm gears on the ends of the worm shafts, a star wheel secured to one end of each second named worm shaft, two pins movably secured to a stationary part and normally held in retracted position, and means for moving the pins into the path of the star wheels whereby the latter will be turned about their axes through a small angle every time they pass a pin, one pinbeing. located inside of the circle formed by the centers of the star wheels when the propeller is rotating and the other being located outside of this circle.

2. A variable pitch propeller comprising, in combination, a hub having a plurality of radial arms of cylindrical shape, a propeller blade attachedvto each arm, the root portion of each blade having a cylindrical opening adapted to receive the arm, the propeller blade having an opening extending transversely therethrough, that part between the bottom of the circular opening and the transverse opening having an opening concentric with, but of smaller diameter than the circular opening, the outer end of each arm having a portion of reduced diameter extending into the transverse opening where it is provided with a nut and an antifriction bearing between the nut and the material of the blade.

3. A variable pitch propeller comprising, n combination, a propeller shaft, a hub secured thereon, propeller blades carried by the hub and mounted for rotation about their axes and means for turning the blades, said means comprising an assembly removably connected with the hub, said assembly comprising a bearing block and a worm shattand worm mounted for rotation therein.

4. A variable pitch propeller comprising, in combination, a propeller shaft, a hub secured thereon, propeller blades carried by the hub, said hub carrying thereon a separate assembly block with self-contained mechanism designed to serve as anintermediaryv to communicate and cause change of pitch of the propeller blades, within time periods relative to the revolutions per minute of the propeller;

5. A variable pitch propeller comprising, in combination, a propeller shaft, a hub secured thereon, a propeller blades carried by the hub, said hub carrying thereon a separate assembly block or unit with self-contained mechanism designed to serve as an intermediary to communicate and cause change of pitch of the propeller blades, within time p e riods relative to and based on the revolving propeller, said mechanism being activated by operating devices projected as liasions, substantially as shown and described.

6. A variable itch propeller comprising, a hub having su stantially radial cylindrical arms, a propeller blade secured to each 

